Re: [PATCH v2 4/5] ARM: dts: omap5: describe control for ckobuffer

[Tero Kristo]

On 27/04/16 09:04, H. Nikolaus Schaller wrote:
> > Am 26.04.2016 um 19:27 schrieb Tony Lindgren <tony@xxxxxxxxxxx>:
> >
> > Tero,
> >
> > * H. Nikolaus Schaller <hns@xxxxxxxxxxxxx> [160418 11:23]:
> > > OMAP5 has a register to control if the ckobuffer is enabled
> > > and defines the polarity. ckobuffer is required to drive a twl6040
> > > with the system clock. Hence, add the pinctrl,single to the
> > > OMAP5 SoC description so that omap5-board-common can
> > > set up the ckobuffer as required.
> >
> > Is this really a mux or should it be a mux clock?
>
> It is a pinmux setting for the clock out buffer to choose what signal
> (and polarity) is presented on the fref_xtal_clk pad.
>
> The register is part of the CTRL_MODULE_WKUP.
> The clock signal is the xtal master clock of the whole SoC.
>
> Although there is a bit to choose an alternate clock, there is no
> alternate in the OMAP5 silicon.
>
> Therefore I would say it is about padconf and not clock or clock mux
> related.
>
> It just happens to be a clock signal which can be routed to this
> pad.

The two could very well be implemented as clock nodes, a mux and a gate. 
This would describe the hardware functionality better imo, if the 
assumptions made here are correct. Implementing the control as pinctrl 
hacks looks rather weird to me.

I could not find any documentation related to the ckobuffer usage 
though, maybe Peter can provide some insight? I think you spent some 
considerable time bringing up twl6040 a few years back...

-Tero

> BR,
> Nikolaus
>
> > Regards,
> >
> > Tony
> >
> > > Signed-off-by: H. Nikolaus Schaller <hns@xxxxxxxxxxxxx>
> > > ---
> > > arch/arm/boot/dts/omap5.dtsi | 10 ++++++++++
> > > 1 file changed, 10 insertions(+)
> > >
> > > diff --git a/arch/arm/boot/dts/omap5.dtsi b/arch/arm/boot/dts/omap5.dtsi
> > > index 120b6b8..1d9050f 100644
> > > --- a/arch/arm/boot/dts/omap5.dtsi
> > > +++ b/arch/arm/boot/dts/omap5.dtsi
> > > @@ -277,6 +277,16 @@
> > > 				pinctrl-single,register-width = <16>;
> > > 				pinctrl-single,function-mask = <0x7fff>;
> > > 			};
> > > +
> > > +			omap5_control_ckobuffer: pinmux@cdb4 {
> > > +				compatible = "ti,omap5-padconf",
> > > +					     "pinctrl-single";
> > > +				reg = <0xcdb4 4>;
> > > +				#address-cells = <1>;
> > > +				#size-cells = <0>;
> > > +				pinctrl-single,register-width = <32>;
> > > +				pinctrl-single,function-mask = <0xf0000000>;
> > > +			};
> > > 		};
> > >
> > > 		ocmcram: ocmcram@40300000 {
> > > --
> > > 2.7.3